The present invention relates to an imaging device such as a copy machine, printer and the like for forming an image on a recording paper.
Recently, many imaging devices such as copy machines, printers and the like for forming an image on a recording paper use an electrophotographic method.
In the electrophotographic method, the surface of a uniformly charged electrostatic photoconductive material is exposed; a latent image is formed to a portion of the photoconductive material from which electric charges are removed; toner is deposited to the latent image to form a toner image (visible image); and then this toner image is transferred onto a recording paper.
This imaging device making use of the electrophotographic method such as, for example, a laser beam printer is provided with a cylindrical photoconductive drum having a surface formed of an electrostatic photoconductive material. The photoconductive drum is rotated at a predetermined circumferential speed. There are disposed around the photoconductive drum as a center a cleaning mechanism for cleaning toner remaining on the surface of the photoconductive drum; a corona changer for uniformly charging the photoconductive material on the surface of the photoconductive drum; a scanning optical system for exposing and scanning the surface of the photoconductive drum with a laser beam turned ON and OFF in response to image information; a development unit for depositing toner to a portion of the photoconductive material from which electric charges are removed by exposure and made to a latent image and making the latent image to a toner image; and a transfer charger for charging a recording paper and transferring the toner image thereon, respectively. Further, a fixing unit for fixing the toner image on the recording paper is disposed at a location to which the recording paper onto which the toner image is transferred by the transfer charger is fed.
Further, the copy machine is provided with a scanning and irradiating unit for scanning and irradiating a document placed on a document placing unit in place of the above scanning and optical system; and an optical system for introducing a light reflected from the document irradiated by the scanning and irradiating unit onto the surface of a photoconductive drum.
The above imaging device making use of the electrophotographic method has such a complex process that a latent image is formed by irradiating the photoconductive material of a photoconductive drum with a light having image information and the latent image is developed by being deposited with toner and further transferred onto a recording paper. Thus, a problem arises in that the structure of the 1mating device is made inevitably complex due to the complex processes and the size of the imaging device is difficult to be reduced.
On the other hand, recently, a photoconductively-color-changing agent is developed and attracts attention as toner to be used for image formation. The photoconductively-color-changing agent; usually exhibits a specific color and when irradiated with a light having a specific wavelength, this color is irreversibly changed to colorless and transparent. An article entitled "Trends." in "NIKKEI MECHANICAL" dated Jul. 22, 1991 discloses such a photoconductively-color-changing agent.
This photoconductively-color-changing agent includes, for example, a mixture of cyanine type pigment exhibiting blue color IR820B and organic born ammonium salt. When near infrared rays of 820 nm are irradiated to the photoconductively-color-changing agent, the blue color disappears and the photoconductively-color-changing agent becomes colorless and transparent. This phenomenon is described as follows. That is, the IR820B absorbs the near infrared rays having the wavelength of 820 nm and thus the characteristic of the IR820B to selectively reflects only a blue monochromatic light is changed to cause lights of all the wave lengths to pass therethrough. At this time, the organic boron ammonium salt acts as a catalyst to make this phenomenon irreversible.
When this photoconductively-color-changing agent is used as toner by an imaging device making use of the electrophotographic method for the formation of an image, it is contemplated to irradiate a light having a specific wavelength to a recording paper onto which information has been recorded and to cause the information disappear therefrom so that the recording paper can be used again. However, there has been no idea to provide a novel imaging device by making use of the photoconductively-color-changing agent.